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Vehicle damage to vegetation of the Rangipo Desert, Tongariro National Park, National Park, New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of MSc in Ecology, Massey University, Turitea, Palmerston North, New Zealand

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Abstract

Rangipo Desert, Tongariro National Park, Central North Island, New Zealand,
contains one of New Zealand’s unique habitats due to the desert-like environment
containing cushions, low lying species, and native grasses which create a diverse
mosaic of plant species and colour. This area is under anthropogenic threat from
drivers operating vehicles over the vegetation. My aim was is investigate the damage
to vegetation and substrates which have been driven over by vehicles.
Aerial images were used to draw information about the Desert’s ecosystem, and
driver’s manoeuvring preferences which were ground-truthed. A Canonical
Correspondence Analysis was used to evaluate the accuracy of categories from the
aerials after ground-truthing. A Paired t test was used to show varying vegetation
densities against other tested variables. A Chi Square Analysis was used to examine
where drivers preferred to drive. The results indicate drivers prefer to drive over bare
substrate and sparsely vegetated areas within the desert, avoiding dense vegetation,
deeply cut channels and rough, un-driveable terrain.
The direct damage done by vehicles to vegetation and surrounding substrate was
tested by running a simulated tyre over the substrate and plants. A plant having had
a tyre pushed over it by hand was compared to a plant that had been previously
damaged by vehicles, and a control (undamaged) plant. Analysis of Variance was
used to test differences in the growth of the plants within each treatment and the
change in topography. There is evidence of plant damage; however, different
species reacted differently to treatments, depending on which variable was being
tested, making it difficult to identify which species are most affected by vehicle
damage.
The tyres alter the substrate instantly. Intact and broken substrates were compared
by creating wind and rain with a leaf blower and watering can. The change in
substrate height was measured and Analysis of Variance was used to test the
amount of substrate erosion. Results show broken substrates are eroded at a
greater rate than intact substrates, and the erosion rate is increased when the
substrate is dry. Wet, sandy substrates in windy conditions and wet, pumice
substrates in rain have the lowest amount of substrate movement after damage.
The Rangipo Desert’s dry and open ecosystem and vegetation is vulnerable to
damage from vehicles. Vehicles cause plant die-back, increase erosion and have the
potential to change the current ecosystem. Preventing vehicles driving into the
Desert, and educating members of the public about ecosystem damage are good
starting points to manage and preserve this area of Tongariro National Park.
KEYWORDS Arid ecosystems, vehicle damage, erosion, plant changes, microtopography.